High frequency electron discharge device



July 23, 1968 J. K. MANN 3,394,283

HIGH FREQUENCY ELECTRON DISCHARGE DEVICE July 23, 1968 J. K. MANN3,394,283

HIGH FREQUENCY ELECTRON DISCHARGE DEVICE Original Filed Deo. 16, 1959 2Sheets-Sheet 2 Afrarney United States Patent O 3,394,283 HIGH FREQUENCYELECTRON DISCHARGE DEVICE Joseph K. Mann, Palo Alto, Calif., assigner toVarian Associates, Palo Alto, Calif., a corporation of CaliforniaApplication .lune 18, 1962, Ser. No. 203,374-, now Patent No. 3,309,631,dated Mar. 14, 1967, which is a division of application Ser. No.859,964, Dec. 16, 1959, now Patent No. 3,058,026, dated Uct. 9, 1962.Divided and this application Nov. 25, 1966, Ser. No. 597,085

4 Claims. (Cl. 315-548) ABSTRACT F 'I1-IE DISCLOSURE A multi-cavityklystron tube employing a simplified modular construction in which themodules are the tuued cavities. The cavities, including tiat circularend walls are tirst assembled and then two or more cavities are joinedtogether by brazing the mating end walls together around theirperipheries. Within each of the cavities is mounted a simplified tunermechanism incorporating stops to limit the travel of the movablemembers.

This application is a divisional application of co-pend ing U.S. patentapplication, Ser. No. 203,374, now U.S. Patent 3,309,631 issued Mar. 14,1967 led June 18, 1962 which in turn is a divisional application ofUnited States patent application Ser. No, 859,964 tiled Dec. 16, 1959now United States Patent No. 3,058,026 issued Oct. 9,

The present invention relates in general to high frequency tubeapparatus, and, more specifically, to a novel high frequency, high powervelocity modulation tube which is extremely useful for providing acontinuous wave output at high average powers and which is easilytunable over a wide frequency range. Such tubes are especially useful asoutput tubes in tropospheric forward scatter communication link, and fortransmitting tubes covering the UHF-TV band.

Heretofore multicavity klystron ampliiiers have been built which wouldprovide relatively high output powers on the order of one kw. average atS frequency band. These tubes suffered from short life and complexity.

The present invention provides -a compact, rugged permanent magnet, aircooled, high power, multicavity klystron amplifier capable of deliveringaverage output powers in the order of one or more kw. and at the sametime have the greatly enhanced tuning range of approximately 40 percentand a gain of 50 db. The wide tuning range is obtained by the use of animproved tuning apparatus first disclosed in the co-pending application,Ser. No. 749,225, now U.S. Patent No. 2,994,009, invented by Robert C.Schmidt et al. and wherein both the inductive and the capacitiveparameters are varied in a desired manner to tune the cavity.

The principal object of the present invention is to provide a novel highpower, high gain amplilier tube apparatus having exceptionally widefrequency tuning range.

One feature of the present invention is the provision of a novel tuneractuator apparatus whereby the tuner means can easily be positioned andadjusted within the cavity as desired.

Another feature of the present invention is the provision of a novelhigh frequency tube assembly including a plurality of cavity resonators,each reso-nator having two spaced apart circular end walls and sidewallstherebetween, the end walls of successive resonators being joinedtogether in a vacuum tight manner at their periphery whereby separatecavity resonators can be tirst separately ICC assembled and then thedesired number of separate assembled cavity resonators successivelyjoined together.

Other features and advantages of the present invention will becomeapparent upon a perusal of the following specification taken inconnection with the accompanying drawings wherein,

FIG. 1 is a partly cut away side elevational View of a novel high powerklystron amplifier of the present invention,

FIG. 2 is an enlarged detailed view of a portion of the structure ofFIG. 1 delineated by line 2 2,

FIG. 3 is an enlarged cross-section view of a portion of the structureof FIG. 1 taken along line 3-3 in the direction of the arrows with thetuning means shown in its most inward postion,

FIG. 4 is a cross-section view of a portion of the structure of FIG. 3taken along line 4-4 in the direction of the arrows, and

FIG. 4a is a cross-section view of the tuner portion of the structure ofFIG. 4 with the tuning means shown in its most outward position.

Referring now to the drawing, there is shown in FIG. l the external,`partially cut away configuration of the novel tube apparatus of thepresent invention. More spe cically, a segmented tubular cathodeassembly 11 provides a source of electrons which are formed into apencil-like beam and projected longitudinally of the tube apparatus. Aplurality of substantially rectangular cavity resonators, including aninput cavity 12, second and third cavities 13 and 14, and an outputcavity 15 are centrally apertured to allow the passage of thepencil-like beam of electrons therethrough.

The individual cavity resonators 12-15 are tunable over a wide range viaa plurality of novel tuner assemblies 16 which will be more fullydescribed below. The beam, after passing through the output cavityresonator 15, is collected in a collector assembly 17. The thermalenergy generated by the impinging electrons within the collectorassembly 17 is carried away by an air stream circulated about thecollector assembly 17.

R.F. signal energy, which it is desired to amplify, is fed to the inputcavity 12 by a vacuum sealed coaxial connector 1S. The signal energyvelocity modulates the beam as it passes through the input cavity 12.Velocity modulation of the beam is transformed into current densitymodulation in drift spaces between the input cavity 12 and the irstbuncher cavity 13. The buncher cavities 13 and 14 further velocitymodulate the beam to produce greater current density modulation of thebeam at the output cavity 15. The output cavity extracts R.F. energyfrom the current density modulated beam.

The output RF. energy is coupled outwardly of the output resonator 15via a vacuum sealed R.F. coaxial line 19 described in detail below andis fed to a suitable load, not shown, such as, for example, an antenna.A permanent magnet comprising two shell-shaped magnet sections 21 boltedtogether by bolts 21a and clamped onto a pole piece at each end of thetube apparatus, containing the cavity resonators, surrounds the centralpart of the tube apparatus on two sides and provides a strong axialmagnetic iield longitudinally of the tube for confining the pencil-lil ebeam of electrons. Each of the magnet sections 21 is provided with ahandle 2lb for lifting the tube assernbly with the magnet attachedthereto.

The novel wide range tuner assembly 16 of the present invention is shownin greater detail in FIGS. 3 and 4. More specifically, an inductanceplate 22, as of copper, has two thin conductive diaphragms 23 as of0.015 thick OFI-IC copper :sheet fixed thereto as by brazing alongopposite sides of the plate 212. The other ends of the diaphragms 23 areixedly secured as by brazing to the cavity end walls 24. The inductanceplate 22 is provided with a forwardly projecting block portion midwaybetween the diaphragms 23 whereby when the inductance plate 22 is in itsforwardmost position, the forwardly projecting block -portion 25 and thefolds of the diaphragms 23 substantially form a partition across thecav-ity resonator which opens up When the inductance plate is movedrearwardly, as shown in FIG. 4 r1.

The inductance plate 22 with its associated diaphragms 2.3 serves tovary predominately the inductive parameter of the cavity resonator :bydisplacing the magnetic field. Since in the most rearward position ofthe inductance plate 22 the volume within the folds of the diaphragm 23is opened up for the magnetic field to penetrate whereas the volumewithin these folds is effectively closed off with the inductance platein its foiwardmost position, this novel inductive tuner allows a fasterirate of change of inductance than does the conventional inductive tunerplate which is completely fiat.

A curved capacity plate 26 including two parallel side portions 27connected in their midportions by a strap 28 is canried upon theextremity of a capacity support arm 29 which in turn is carried from theinductance plate 22. The capacity plate 26 is longitudinallysymmetrically disposed with respect to the `re-entrant portions of thedrift tubes 31 within the cavity resonators with the strap 23 positionedat the gap between the drift tubes 3l and is positioned on the oppositeside of the drift tubes 3i from the inductance plate 22. The capacityplate 26 serves to vary predominately the capacitive loading between themutually opposed and spaced apart re-entrant portions of the drift tubes17. This capacity plate 26 is curved to conform to the externalconfiguration of the drift tubes 31 thereby to conform to the directionof the magnetic field lines within the cavity to tune the cavityinductively as little as possible and decrease the Reh/Q a minimumamount. At the low frequency end of the tuning range of the tuningassembly when the capacity plate 2.6 is closest to the dlilift tubes 31,the particular configuration of the capacity plate prevents the tuningrate due to the capacity plate 26 from increasing rapidly as thecapacity plate nears the drift tubes 31. This is 'so because when theside portions 27 of the capacity plate 26 are close to the drift tubes,most of their movement is substantially parallel to the closest surfacethereof, whereas the only portion of the capacity plate 26 movingdirectly toward drift tubes 31 is the nairrow strap 28 connecting theside yportions 27. Furthermore, with the strap 28 positioned at the gapbetween the drift tubes 31, the input and output members of the tubewhich are located in the cavity wall opposite the tuner assembly areshielded from a direct View of the electron beam, thereby preventingbreakdown of the ceramic R.F. seals due to impact of electrons firom theelectron beam. Since the capacity plate 26 is disposed on the oppositeside of the re-entrant portions of the drift tubes 31 from theinductance plate 22, inward movement of the inductance plate 22 servesto decrease the inductance of the cavity and also to decrease thecapacitance of the cavity. Conversely, when the inductance plate 22' ismoved outwardly of the cavity resonator, Iboth the inductance and thecapacitance are increased. Thus, both the inductive and capacitiveparameters of the cavity are being simultaneously varried in acomplementary way to obtain large tuning effects with relatively smallchanges in the position of the tuning members.

For actuating the tuner means, an inwardly threaded hollow cylindricaltuner nut 32 is xedly secured to the backside of the inductance plate 22by means of an annular flange member 33 brazed to the inductance plate22 and capturing an outwardly projecting flange on the end of the tunernut 32. A `hollow cylindrical tuner bearing member 34 is constricted atone end to `act as a bearing for the outside surface of the tuner nut 32with the other end of the bearing member extending away from the tunernut and provided with an outwardly extending flange 34a to position thebearing member 34 within the cavity, `as described in detail below. Atuner screw 35 is provided with scirew threads on one end thereof, whichengage the inner threads of the tuner nut 32, and an annular shoulder 36projecting outwardly from the tuner screw 35 is rotatably captured in anannular recess in the flange 34a on the tuner bearing member 3d by aretaining ring 37. An inwardly threaded hollow cylindrical tuner stop 33slidably ts within the tuner bearing member 34, is screwed onto the freeend of the tuner nut 32, and is locked in place by a set screw 39.Rotation of the tuner screw `35 provides longitudinal movement to thetuner nut 32 held within the bearing end of the tuner bearing member 34,the forward longitudinal movement being limited by the tuner stop 38 andthe rearward movement being limited by the annular ange member 33 on theback of the inductance plate 22.

As an indication of the position of the tuner within the cavity, a tunerindicating means passes axially through the tuner nut 32- and the tunerscrew 35. This tuner indicating means includes a threaded rod 50ipositioned within a bore through the tuner screw 35 and screwed into aplate 4l positioned within the end of the tuner nut 32 adjacent the backof the inductance plate 22. A tuner indicator 42 provided with indicatorrings 43 along the external length thereof is screwed onto the other endof the rod 40 and is iixedly held in place by a set screw 44 screwedtherewithin and abutting the end of the rod 40. As the tuner is movedwithin the cavity, the length of the tuner indicator 42 projectingoutside of the tuner sorew 35 is changed and the position of the tuneris thereby indicated by the indicator rings 43.

A U-shaped cavity isidewall member 45 ias of copper, is iixedly securedbetween the two end Walls 24 of each cavity as by brazing, and providesthree of the sidewalls of the cavity. The fourth sidewall member 46 asof coppe-r, is provided with an aperture therethrough for passage of thetuner assembly 16 and is fixedly secured as by brazing to the end walls24 and the ends of the sidewall 45S. A ring 47 as of Monel is vacuumsealed as by brazing within the aperture in the fourth sidewall 46 formounting the tuning assembly and maintaining the vacuum seal.

The tuner bearing member 34 slidably fits within the ring 47 and isbolted thereto by means of a plurality of cap screws 4S which passthrough the retaining ring 37, through the flange 34a on the end of thetuner bearing member 34 and into tapped holes circularly spaced aboutthe ring 47. A plurality of set screws 49 are threaded into tapped holescircularly spaced about the flange 34a and bear up against the ring 47.By proper adjustment of these set screws 49, the entire tuner assemblycan be positioned within the cavity so that the tuner members areproperly spaced from the cavity walls and the tuner means is properlypositioned to cover the desired tuning range.

A flexible metallic bellows 51 as of stainless steel is ixedly securedin a vacuum tight manner at one end thereof to the outside periphery ofthe ring 47 within the cavity and at the other end thereof to theoutside periphery of the annular flange member 33 on the inductanceplate 22. The bellows 51 serve as a flexible vacuum seal for sealing thetuner actuating mechanism from the tuning elements disposed within thecavity resonator thereby permitting translation of these tuning elementswithin the cavity without destroying the vaccum integrity thereof.

The cavity resonators i2, i3, 14 and l5 are successively arranged alongthe beam path for successive electromagnetic interaction with the beamof electrons passable therethrough. The separate cavity resonators aresealed together in a vacuum tight manner via a heliarc weld at theperiphery of the end plates 24 of adjacent cavity resonators.

An output coupling loop is formed by a strap 52 as of Copper vacuumsealing the end of the hollow center conductor 53 ol the output coaxialline i9 and connecting this center conductor 53 to the outer conductor54. Near its external end the outer surface of the outer conductor 54 isprovided with a shoulder which engages a cooperating shoulder on ahollow cylindrical member 55 as of copper which surrounds the outerconductor and is vacuum sealed within an output port S6 in the outputcavity 15. The external ends of the outer conductor 54 and thecylindrical member 55 are vacuum sealed together as by brazing. v

An annular wave permeable window member 57 of ceramic as, for example,alumina is coaxially disposed with respect to the inner and outerconductors 53 and 54 and vacuum sealing the space therebetween as bybrazing. The thickness and position of the window 57 are selected topresent a predetermined discontinuity in the transmission line and thedesired discontinuity can easily be achieved by the use ofV aluminaceramic which has low loss and a` higher dielectric constant on theorder of 9 as compared with a dielectric constant of about 3 to 6 forglass previously used for wave permeable windows.

Thus, the ceramic window 57 serves to form the vacuum seal for the R.F.outputas well as a frequency sensitive impedance transformer whichtransforms the load impedance to the optimum impedance for the tube atall frequencies of operation.

This novel window requires no adjustment over the range of the tube, asfrequently required in the past, or the necessity for matched window aspreviously used in combination with a loading member.

A hollow cylindrical output coupling ange S9 for bolting the coaxialline 19 to a standard lS/s coaxial line 59 by means of a bullet typeadaptor assembly 60 surrounds the cylindrical member S5 and is lixedlysecured thereto by cap screws on a split ring member 61 which fitswithin an annular recess in the outside surface of the cylindricalmember 5S. An outer conductor extension 62 slidably fits within theexternal end of the outer conductor 54, seats against a shoulder on theinside surface of the outer conductor 55 and bears against the outerconductor of the coaxial line 59. In this manner nothing bears againstthe vacuum sealed joint between the outer conductor S4 and thecylindrical member 55 so that the force of shocking blows is notdirected against this seal.

The collector assembly 17 serves to collect the electron beam after itpasses through the output cavity 15. In the collector assembly 17, acollector pole piece 63 as of steel is secured to the end wall of theoutput cavity in a vacuum tight manner by means of annular flanges 63asecured together by means of a heliarc weld. A hollow cylindricalcollector 64 as of steel is secured at one end thereof to the pole piece63 and near the other end to a circular plug member 65 as of copperprovided with a circular groove on either side thereof, these groovesbeing radially spaced from one another to allow for differentialexpansion between the collector 64 and the plug member 65. A circularplate 66 as of steel covers the ends of the collector 64. The steelcollector minimizes the magnetic field within the collector to preventfocusing of secondary electrons back into the resonator section of thetube apparatus. A plurality of radially extending fins 64a fixedlysecured to the collector 64 substantially over the length thereofprovide means for dissipating the collector heat by means of an airstream.

Since many changes can be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A tuner mechanism for accurately adjusting the position of a tuningmember within a cavity comprising an inwardly threaded hollowcylindrical tuner nut connected at one end to the tuning member; ahollow cylindrical tuner bearing member constricted at one end to act asa bearing for the outside surface of said tuner nut, the other end ofsaid bearing member extending away from said tuner nut and adjustablyattached to the cavity; a tuner screw adapted to engage the innerthreads of said tuner nut and to impart longitudinal movement to saidtuner nut and thus to said tuner member, and tuner stop means secured tothe end of said tuner nut within said tuner bearing member the outsidediameter of said tuner stop means being greater than the inside diameterof said constricted portion of said bearing member where- -bylongitudinal movement of said tuner nut is limited to a particulardistance, inward movement of tuner member being limited when said tunerbearing constricted portion contacts said tuner stop means and outwardmovement of said tuner member being limited -when said tuner bearingmember contacts the back of said tuner member whereby the length of thetuner movement can be adjusted by the position of said tuner stop meansand the position of said tune-r means at the end of its travel can beadjusted by adjusting the position of said bearing member with respectto said cavity.

2. An electron discharge device including means for forming an electronbeam; means for collecting the electron beam; cavity resonator meansdisposed between the means for forming the electron beam and the meansfor collecting the electron beam; means for tuning said cavity resonatormeans; and output coupling means for coupling the KF, energy from saidcavity resonator means to 'a load; said cavity resonator means includinga plurality of axially aligned cavity resonators adapted forelectromagnetic interaction with the beam of electrons passabletherethrough, each of said cavity resonators including two spaced apartcircular end walls provided with an aperture therethrough adapted topass the beam of electrons, a drift tube projecting inwardly to each ofsaid cavity resonators from eac-h of said spaced apart end walls andpositioned within the apertures through said end walls, side wallportions connected to said spaced apart end walls enclosing theremainder of each of said cavity resonators, the end walls of successivecavity resonators being joined together at their periphery in a vacuumtight manner -whereby each of the separate cavity resonators is lirstseparately assembled and the desired number of separate cavityresonators successively joined together; said means for tuning saidcavity resonator means -including a tuner mechanism for accuratelyadjusting the position of a tuning member -within each of said cavityresonators comprising an inwardly threaded hollow cylindrical tuner nutconnected at one end to the tuning member; a hollow cylindrical tunerbearing member having a constricted portion at one end to act as abearing for the outside surface of said tuner nut, the other end of saidbearing member extending away from said tuner nut and adjustablyattached to the cavity resonator; a tuner screw Vadapted to engage theinner threads of said tuner nut and to impart longitudinal movement tosaid tuner nut and thus to said tuner member, and tuner stop meanssecured to the end of said tuner nut within said tuner bearing member,the outside diameter of said tuner stop means being greater than theinside diameter of said constricted portion of said bearing memberwhereby longitudinal movement of said tuner nut is limited to aparticular distance, inward movement of tuner Vmember being limited whensaid tuner bea-ring constricted portion contacts said tuner stop meansand outward movement of said. tuner member being limited when said tunerbearing member contacts the back of said tuner member whereby the lengthof the tuner movement can be adjusted by the position of said tuner stopmeans and the position of said tuner means at the end of its travel canbe adjusted by adjusting the position of said bearing member withrespect to said cavity resonator.

3. High frequency tube apparatus including a plurality of axiallyaligned cavity resonators adapted for electromagnetic interaction with abeam of electrons passable therethrough, each of said cavity resonatorsincluding two spaced apart circular end walls provided with an aperturetherethrough adapted to pass the beam of electrons, a drift tubeprojecting inwardly to each of said cavity resonators from each of saidspaced apart end Walls and positioned within the apertures through saidend Walls, side wall portions connected t0 said spaced apart end Wallsenclosing the remainder of each of said cavity resonators, the end wallsof successive cavity resonators being joined together at their peripheryin a vacuum tight manner whereby each of the separate cavity resonatorsis rst separately assembled and the desired number of separate cavityresonators successively joined together.

4. A high frequency tube apparatus including, means for producing anddirecting a beam of charged particles over a predetermined pathlongitudinally of the tube, means for collecting the beam at theterminating end of the beam path, and a plurality of axially alignedcavity resonators disposed along said beam path for producing successiveelectromagnetic interaction with said beam and for extracting highfrequency energy from said beam,

each of said cavity resonators including two spaced apart circular endwalls provided with an aperture therethrough adapted to pass said beamof electrons, a drift tube projecting inwardly of each of said cavityresonators from each of said spaced apart end Walls and positionedwithin the apertures through said end walls, side wall portionsconnected to said spaced apa-rt e-nd wall portions enclosing theremainder of each of said cavity resonators, the end walls of successivecavity resonators being joined together at their periphery in a vacuumtight manner whereby each of the separate cavity resonators is firstseparately assembled and the desired number of separate cavityresonators successively joined together.

References Cited UNITED STATES PATENTS 2,994,009 7/1961 Schmidt et al.315-548 3,016,501 l/l962 Gardner et al. 315-553 X 3,169,206 2/1965Nelson S15- 5.46 X

HERMAN KARL SAALBACH, Primary Examiner.

S. CHATMON, IR., Assistenti Examiner.

